JPS61254975A - Transparent hologram - Google Patents

Abstract

PURPOSE:To increase its transparency and the intensity of reflected light by forming a continuous transparent thin film which has a larger refractive index than a hologram layer on the relief formation surface of the hologram layer. CONSTITUTION:A transparent hologram is constituted as a relief hologram and the hologram layer 2 is formed on the surface so that interference fringes corresponding to the wave front of light from an object for a pattern of projections and recesses. Namely, the relief formation surface 3 is provided. Further, the continuous transparent thin film 4 which has a larger refractive index than the hologram layer 2 is formed on the formation surface 3 in conformity with the shape of the projection-recess pattern. Thus, the transparency and the intensity of the reflected light are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in relief holograms, and more particularly to transparent holograms that are transparent themselves but also have the characteristics of reflection holograms.

[Conventional technology]

One method for recording holograms is to record interference fringes, which correspond to the wavefront of light from an object, using an uneven pattern on the surface of the material.The relief holograms obtained by this method can be easily reproduced in large quantities using press technology. There is an advantage that it can be done.

Today, various attempts are being made to form relief holograms on base materials such as credit cards, cash cards, book covers, record jackets, etc., and these relief holograms can be used as base materials by methods such as transfer, pasting, and direct formation. When integrated into materials, reflected light intensity becomes an important issue. Generally, since relief holograms are made of synthetic resin, the intensity of reflected light at the relief forming surface, that is, the interface between the resin and air having a difference in refractive index, is small, and therefore the hologram effect is small.

For example, when a relief hologram is formed using a resin with a refractive index of n=1.5, the reflectance R on the relief forming surface is very low (R=4%) according to Fresnel's formula, and the hologram effect is insufficient. be.

Therefore, in the past, reflective metal thin M with a reflectance of 90% or more was used.
Efforts have been made to increase the intensity of reflected light by forming a thin film of aluminum (for example, an aluminum thin film) on the relief forming surface by vapor deposition, thereby creating a sufficient hologram effect, and most of the so-called reflection holograms are of this type. The structure is adopted.

[Problem that the invention seeks to solve]

However, in conventional holograms in which a reflective metal thin film is formed on the relief forming surface, even if a pattern layer is printed on the back side of the metal thin film, the light waves propagating through the metal thin film are attenuated in the traveling direction. Because the hologram was folded away, the pattern layer could not be seen, and it was not possible to improve the appearance of the hologram forming surface from a design perspective.

In addition, metal thin films are usually silvery white and have high brightness, so there is a problem that it looks strange when holograms are placed on various substrates such as cards and book covers. Improvement was desired.

The present invention has been made in view of the above points, and an object of the present invention is to provide a transparent hologram that is transparent and has a large reflected light intensity, that is, can exhibit a sufficient hologram effect.

[Means for solving problems]

The transparent hologram of the present invention is a relief hologram having a hologram layer on the surface of which interference fringes corresponding to the wavefront of light from an object are formed as an uneven pattern, and the hologram layer is formed on the relief forming surface of the hologram layer. It is characterized by forming a transparent continuous thin film having a refractive index larger than the refractive index.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, l indicates a transparent hologram of the present invention,
The hologram 1 is configured as a relief hologram,
It has a hologram layer 2 on the surface of which interference fringes corresponding to the wavefront of light from an object are formed in an uneven pattern.

In this way, the hologram layer 2 has an uneven pattern surface on which interference fringes are formed as an uneven pattern, that is, a relief forming surface 3, and the relief forming surface 3 has a refractive index larger than that of the hologram layer 2. A transparent continuous thin film 4 is formed along the shape of the uneven pattern.

In the present invention, the material of the hologram layer 2 is polyvinyl chloride, acrylic (e.g. MMA), polystyrene, thermoplastic resin such as polycarbonate, unsaturated polyester, melamine, epoxy, polyester (meth)acrylate, urethane (meth)acrylate. , epoxy (meth)acrylate, polyether (meth)acrylate,
Cured thermosetting resins such as polyol (meth)acrylate, melamine (meth)acrylate, and triazine acrylate, or mixtures of the above-mentioned thermoplastic resins and thermosetting resins can be used.

Furthermore, as the material for the hologram layer 2 of the present invention, thermoformable Thff having a radically polymerizable unsaturated group can be used, and there are two types of this: Thff.

(1) A polymer having a glass transition point of 0 to 250°C and having a radically polymerizable unsaturated group. More specifically,
As the polymer, a product obtained by polymerizing or copolymerizing the following compounds (1) to (2) and introducing a radically polymerizable unsaturated group by methods (a) to (d) described below can be used.

■ Monomers having hydroxyl groups 2N-methylolacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2
-Hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, 2-hydroxy-3-phenoxypropyl methacrylate, 2-hydroxy-3-phenoxypropyl acrylate, etc.

■ Monomers with carboxyl groups such as nialic acid, methacrylic acid, acryloyloxyethyl monosuccinate, etc.

■ Monomer nigericidyl methacrylate, etc. having an epoxy group.

(2) Monomers having an aziridinyl group: 2-aziridinylethyl methacrylate, allyl 2-aziridinylpropionate, etc.

■ Monomers containing amino groups such as niacrylamide, methacrylamide, diaseptone acrylamide, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc.

■ Monomer with sulfone group: 2-acrylamide-
2-methylpropanesulfonic acid, etc.

(2) Monomers Having Isocyanate Groups 72. Adducts of diisocyanates and radically polymerizable monomers having active hydrogen, such as 1 mol to 1 mol adducts of 4-toluene diisocyanate and 2-hydroxyethyl acrylate.

■Furthermore, in order to adjust the glass transition point of the above copolymer and the physical properties of the cured film, the above compound can be copolymerized with the following monomers that can be copolymerized with this compound. It can also be polymerized. Examples of such copolymerizable monomers include methyl methacrylate, methyl acrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, t-butyl acrylate, and t-butyl acrylate. -Butyl methacrylate, isoamyl acrylate, isoamyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 2
-Ethylhexyl acrylate, 2-ethylhexyl methacrylate, and the like.

Next, the material according to the present invention can be obtained by reacting the polymer obtained as described above by methods (a) to (d) described below to introduce a radically polymerizable unsaturated group. .

(a) In the case of a polymer or copolymer of a monomer having a hydroxyl group, a monomer having a carboxyl group such as acrylic acid or methacrylic acid is subjected to a condensation reaction.

(b) In the case of a polymer or copolymer of monomers having carboxyl groups or sulfone groups, the aforementioned monomers having hydroxyl groups are subjected to a condensation reaction.

(c) In the case of a polymer or copolymer of a monomer having an epoxy group, an isocyanate group, or an aziridinyl group, the above-mentioned monomer having a hydroxyl group or monomer having a carboxyl group is subjected to an addition reaction.

(d) In the case of a polymer or copolymer of monomers having a hydroxyl group or a carboxyl group, s having an epoxy group
A 1:1 mole adduct of a monomer having an aziridinyl group or a diisocyanate compound and a hydroxyl group-containing acrylic acid ester monomer is subjected to an addition reaction.

In order to carry out the above reaction, it is preferable to add a trace amount of a polymerization inhibitor such as hydroquinone and carry out the reaction while blowing dry air.

(2) A compound having a melting point of 0 to 250°C and having a radically polymerizable unsaturated group. Specific examples include stearyl acrylate, stearyl methacrylate, triacryl isocyanurate, cyclohexanediol diacrylate, cyclohexanediol dimethacrylate, spiroglycol diacrylate, and spiroglycol dimethacrylate.

Moreover, in the present invention, the above +11 and (2) can be used in combination, and a radically polymerizable unsaturated monomer can also be added to them.

This radically polymerizable unsaturated monomer improves crosslinking density and heat resistance when irradiated with ionizing radiation, and in addition to the above-mentioned monomers, ethylene glycol diacrylate, ethylene glycol dimethacrylate, Polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, pentaerythritol tetraacrylate, penta Erythritol tetramethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate, ethylene glycol diglycidyl ether diacrylate, ethylene glycol diglycidyl ether dimethacrylate, polyethylene glycol diglycidyl ether dimethacrylate Acrylate, polyethylene glycol diglycidyl ether dimethacrylate, propylene glycol diglycidyl ether diacrylate, propylene glycol diglycidyl ether dimethacrylate, polypropylene glycol diglycidyl ether diacrylate, polypropylene glycol diglycidyl ether dimethacrylate, sorbitol tetraglycidyl ether tetraacrylate, sorbitol Tetraglycidyl ether tetramethacrylate or the like can be used, and O,1
It is preferable to use it in an amount of 100 parts by weight. In addition, although the above materials can be sufficiently cured by electron beams, when curing by ultraviolet irradiation, benzoquinone is used as a sensitizer.
It is also possible to use benzoin ethers such as benzoin and benzoin methyl ether, halogenated acetophenones, and biacyl which generate radicals when irradiated with ultraviolet rays.

Hologram layer 2 can be obtained by conventionally known methods. For example, a hologram master plate on which interference fringes are recorded in the form of unevenness is used as a press mold, a hologram-forming resin sheet is placed on the hologram master plate, and the two are heated and pressure-bonded by means such as a heating roll, so that the hologram-forming resin sheet surface The hologram layer 2 can be obtained by a method of duplicating the uneven pattern of the hologram original plate.

The hologram layer 2 is of a type that can record hologram information through surface irregularities, and specifically, the hologram layer 2 may be one based on the principle of Fresnel hologram, Fourier transform hologram, Fraunhofer hologram, etc., excluding Lippmann hologram. And image holograms, rainbow holograms, etc. that utilize these principles.
Holographic stereograms, holographic diffraction gratings, etc. are used.

The transparent continuous thin film 4 has a refractive index larger than the refractive index of the hologram N2 (usually refractive index: n=1.3 to 1.6), and is similar to providing a conventional reflective metal thin film. 4. Such a thin film can be formed at a location. (Hereinafter, the refractive index: n will be added in parentheses to the right of the material name), 5btsx (n = 3.0), Few (1 + (n
= 2.7), Tilt (n = 2.6), Cd5 (n =
2.6), Ce0z (n=2.3), Zn5 (n=2
．． 3), PbCIz (n112.3), Cd0 (n=2
゜2), 5bzOs (n=2.0), ii (n=2
．． 0), 5iO (n=2.0), BizOs (n-2,
5), InzOs (n□2.o), Pb0 (n=2.6
), Ta,05 (n=2.4), ZnO (n=2.1
), Zr0t (n=2.0), CdzO*(n=1
．． 8) , Alx0s (n=1.6), CaO1iOt
(n=1.8), etc.

The refractive index of the thin film 4 is preferably 0.3 or more larger than the refractive index of the hologram layer 2, and more preferably 0.3 or more.
．． It must be greater than 5. According to experiments conducted by the present inventors, the result is that a value larger than 1.0 is optimal.

The thickness of the thin film 4 may be within the transparent range of the material forming the thin film, but is usually preferably from 100 to 10,000.

As a method for forming the thin film 4 on the relief forming surface 3 of the hologram layer, general thin film forming methods such as vacuum evaporation, sputtering, reactive sputtering, and ion blating can be used.

When a transparent iFi film with a high refractive index is provided in this way, due to the angular dependence of reproduction, which is a characteristic of holograms, outside the angular range in which the hologram can be reproduced, it appears only as a transparent body, and the hologram's reproduction is difficult. Within the angular range, the light reflectance is at its maximum, producing the effect of a reflective hologram.

The hologram of the present invention may include a pattern layer 5 as shown in FIG. The pattern layer 5 can be provided at any position, for example, on the surface of the thin film 4, on the surface of the hologram layer 2, or even on both surfaces of the thin film 4 and the hologram layer 2. The pattern layer 5 is usually formed by printing, and the ink constituting the pattern layer 5 can be any commonly used ink, and any pattern and color can be applied.

In addition to the pattern layer 5, a continuous printed layer may be provided on the surface of the thin film 4 by solid printing in any hue.

Since the thin film 4 is transparent and has a refractive index larger than that of the hologram layer 2, it is possible to obtain necessary and sufficient transparency and reflected light intensity, and as a result, the surface of the thin film 4 The provided pattern layer 5 (in this embodiment, the thin film 4 side is the bottom surface, so the pattern N5 is provided on the bottom surface of the thin film 4) can be seen from the outside, and the hologram effect is also large.

For example, if the refractive index of the resin of the hologram layer is n = 1.4 and the refractive index of the transparent continuous thin film is n = 3.0, then the reflectance R for vertically incident light is R for both P and S polarized waves. =5
0% (however, wavelength of incident light: λ4,000, thickness of transparent continuous thin film: d1,000),
As a result, a sufficient hologram effect can be obtained.

In the present invention, a relief forming surface 3 may be formed on the upper surface of the hologram layer 2, and in this case, a transparent continuous thin film 4 is formed on the lower surface of the hologram layer 2. Further, the thin film 4 is not limited to being formed in a shape that follows the irregularities of the relief forming surface 3, and the lower surface thereof may be flat.

Further, in the present invention, a protective layer 6 can be provided on the lower surface of the thin film 4 and the pattern layer 5, as shown in FIG.

As the material for the protective layer 6, commonly used synthetic resins can be used. Providing the protective layer 6 in this manner not only protects the surface on which the relief is formed and the transparent continuous thin film, but also has the advantage of preventing counterfeiting caused by molding the relief.

Providing a protective layer on the lower surface of the transparent continuous thin film 4 in this way is only possible if there is a transparent continuous thin film 4 as in the present invention. Conventionally, when a protective layer is provided without the transparent continuous thin film 4, Since the refractive index is close to that of the protective layer, the unevenness of the hologram was simply filled in and the hologram could not be reproduced.

Furthermore, in the present invention, the hologram layer and the transparent layer VtTi
Since the 1 film is transparent, instead of providing a pattern on the hologram layer or the transparent Vt3 film, the pattern layer 5 is provided on the surface of a separate support 7 such as paper or plastic, and the adhesive 8 A similar effect can be obtained even if the layers are laminated by any laminating means such as via a wafer (FIG. 3).

The hologram of the present invention can be used for various purposes,
For example, if the hologram of the present invention is provided on cards such as credit cards and cashier cards, the appearance of the cards can be improved.
In addition to novelty, cards that are difficult to counterfeit or alter can be obtained. Also, if it is placed on the cover of a book, record jacket, etc., it will have a rich variety of designs and contribute to improving the value of the product.

Furthermore, since the hologram of the present invention is reproduced only within a specific reproduction angle range, the hologram is not recognized at other normal angles, and when laminated with a separate support, the design of the support and the surface of the support This has the advantage of not interfering with the visual characteristics of the pattern, and eliminates the discomfort that occurs when a conventional reflective hologram having a reflective metal thin film is provided on various substrates.

Further, in the vicinity of the angular range where the hologram can be reproduced, both the hologram and the pattern can be seen by slightly changing the observation position, demonstrating the dual nature of the design.

Next, specific examples of the present invention will be given.

Example A hologram layer (refractive index: n = 1.4) was formed using a mixed resin made by mixing an acrylic resin and a melamine resin at a weight ratio of 4:1, and the relief of the hologram layer was A ZnS thin film (refractive index n+
=2.3) was formed. Vapor deposition conditions are vacuum degree: 10
ZnS was sublimated using a tantalum boat resistance heating method and deposited on the relief forming surface while measuring the thickness using a quartz crystal resonator method.

ZnS density: p = 4.1, Δf = 2,400Hg
Thickness of ZnS thin film after evaporation: dta 1, 20
(thickness: d=2Δ"/ρ). This ZnS
After printing a pattern on the surface, a protective layer (refractive index: nz, 1.
No. 4 resin was used). As a result, it was confirmed that there was a sufficient hologram effect. It was also recognized that the pattern layer was visible from the outside and had excellent transparency.

〔Effect of the invention〕

In the present invention, since a transparent continuous thin film having a refractive index larger than that of the hologram layer is formed on the relief forming surface of the hologram layer, it is possible to obtain necessary and sufficient transparency and reflected light intensity, and as a result, Even when a pattern layer is provided, the pattern layer can be seen from the outside and a sufficient hologram effect can be produced.

Therefore, according to the present invention, a hologram with excellent appearance can be provided by applying various patterns and colors to the picture layer.

Conventionally, when trying to provide a protective layer on the relief forming surface, the difference in refractive index between the hologram layer and the protective layer is almost eliminated, so no reflection, no refraction, and therefore no diffraction occur at the interface, and the hologram effect is lost. However, according to the present invention, the hologram effect does not deteriorate or disappear even if a protective layer is provided on the surface of the transparent Vt thin film. Further, a sufficient hologram effect is exhibited without deterioration or disappearance of the hologram effect due to printing of the pattern layer.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the hologram of the present invention, FIG. 2 is a longitudinal sectional view showing another embodiment of the invention, and FIG. 3 is a support with a pattern layer interposed on the surface of a transparent continuous thin film. It is a longitudinal cross-sectional view showing another example formed by laminating. 2... Hologram layer 3... Relief forming surface 4...
・Transparent continuous thin film

Claims (4)

[Claims] (1) A relief hologram having a hologram layer in which interference fringes corresponding to the wavefront of light from an object are formed as an uneven pattern on the surface, the relief hologram having a refractive index higher than that of the hologram layer. A transparent hologram characterized by forming a transparent continuous thin film having a large refractive index. (2) A transparent hologram according to claim 1, which is formed by printing a pattern layer on the surface of a transparent continuous thin film. (3) The transparent hologram according to claim 1 or 2, wherein a pattern layer is printed and formed on the surface of the hologram layer. (4) The transparent hologram according to any one of claims 1 to 3, wherein a support is laminated on the surface of the transparent continuous thin film via a pattern layer.